Self-retaining packing nut assembly and method for a high pressure pump

ABSTRACT

A self-retaining packing nut assembly may include a first piece having a first and a second section. The first section can be configured to engage diametrically an inside of a pump housing. The packing nut assembly may also include a second piece having a third and fourth section. The third section can engage diametrically an inner surface of the first piece. In addition, the second piece can be configured to axially adjust inside the first piece.

FIELD

The present invention relates to a packing nut assembly, and method thereof, for use in high pressure applications such as hydraulic fracturing.

DESCRIPTION OF THE RELATED ART

The use of high pressure pumps for a variety of different applications is well known in the industry. Some of the most common applications include industrial cleaning, water jet cutting, hydroforming, as well as a wide range of hydraulic applications. Because the components of these pumps are subject to high levels of pressure, they require continuous upkeep, which is both expensive and time consuming. One of the most popular applications of high pressure pumps is in hydraulic fracturing.

A hydraulic pressure pump has both a power end and a fluid end. The power end transmits the necessary power to allow a plunger to reciprocate in the fluid end of the pump. In order to prevent fluid from leaking around the plunger on the power end side of the fluid end housing, a packing is placed in a bore through which the plunger reciprocates in the fluid end housing. The packing creates a seal around the plunger, and acts to prevent fluid from leaking out of the fluid end. This packing is held in place and compressed by a packing nut.

The vibration of the pump, along with the lubrication inserted into the pump, causes the packing nut to loosen and back out of the fluid end housing. Eventually, the packing nut backs out enough to allow the packing to decompress, and fluid begins to leak out of the fluid end housing through the bore of the fluid end housing.

Further, as the packing nut backs out of the fluid end housing, it moves closer to the plunger clamp. Eventually, the packing nut will back out a sufficient amount to where the packing nut and the clamp will collide with one another. This collision has the potential to damage not only the plunger clamp and the packing nut, but also various other components of both the fluid and power ends of the pump. Having to repair the pump after such a collision is both expensive and time consuming, in part because the pump must be inactive during the repair. A user must then take apart the pump and replace the packing nut, and in many instances the packing itself. In other instances, various other parts of the fluid end or the power end housing might need to be replaced.

For the foregoing reasons, there is a need for a self-retaining packing nut assembly that will remain in place, and will not back out of the fluid end pump housing. Such a packing nut assembly needs to be able to withstand the pressure, vibration, and harshness of various applications, including hydraulic fracturing pumping.

SUMMARY

According to certain embodiments, a self-retaining packing nut assembly may include a first piece having a first and a second section. The first section can be configured to engage diametrically an inside of a pump housing. The packing nut assembly may also include a second piece having a third and fourth section. The third section can engage diametrically an inner surface of the first piece. In addition, the second piece can be configured to axially adjust inside the first piece.

An apparatus, according to certain embodiments, may include a housing having a bore along an axis therein, and a plunger configured to reciprocate within the bore along the axis. The apparatus may also include packing at least partially placed between the plunger and a side of the bore, and a self-retaining packing nut assembly in contact with the packing and the housing. The self-retaining packing nut assembly may also comprise a first piece having a first section and a second section. The first section can be configured to engage diametrically an inside of the housing. The packing nut assembly can also comprises a second piece having a third and fourth section. The third section can engage diametrically an inner surface of the first piece. In addition, the second piece can be configured to axially adjust inside the first piece.

According to certain embodiments, a method can include providing a first piece having a first section and a second section, providing a second piece having a third section and a fourth section, and fastening the third section of the second piece to the first piece. The method may also include inserting the first section of the first piece into a pump housing, engaging first piece with the pump housing, and axially adjusting the second piece inside the first piece to compress a packing located inside the pump housing.

BRIEF DESCRIPTION OF THE DRAWINGS

For proper understanding of the invention, reference should be made to the accompanying drawings, wherein:

FIG. 1 illustrates a cross sectional side view of a high pressure pump according to certain embodiments.

FIG. 2 illustrates a perspective view of a self-retaining packing nut assembly according to certain embodiments.

FIG. 3 illustrates a sectional side view of a self-retaining packing nut assembly according to certain embodiments.

FIG. 4 illustrates a sectional side view of the outer ring of a self-retaining packing nut assembly according to certain embodiments.

FIG. 5 illustrates a perspective view of the outer ring of a self-retaining packing nut assembly according to certain embodiments.

FIG. 6 illustrates a sectional side view of the inner ring of a self-retaining packing nut assembly according to certain embodiments.

FIG. 7 illustrates a side view of a slot in the inner ring of a packing nut assembly according to certain embodiments.

FIG. 8 illustrates a perspective view of the inner ring of a self-retaining packing nut assembly according to certain embodiments.

DETAILED DESCRIPTION

Certain embodiments of the present invention relate to a two piece self-retaining packing nut assembly 9 having an outer ring 11 and an inner ring 12 (shown in FIG. 2). Inner ring 12 can be inserted into outer ring 11, while ring 11 positively engages a fluid end housing 1. The embodiment ensures that self-retaining packing nut assembly 9 remains tightly positioned within fluid end housing 1, and that inner ring 12 will not back out of outer ring 11.

In the example shown in FIG. 1, fluid end housing 1 has both a fluid end side A and a power end side B. Power end side B represents the side of fluid end housing 1 that is closer to the power end of the pump (not shown), while fluid end side A represents the side of the fluid end housing 1 furthest from the power end of the pump. Fluid end housing 1 can have an intake/suction valve assembly 2 and a discharge valve assembly 3. A plunger 4 reciprocates axially in the fluid end housing 1 pressurizing an internal fluid chamber 5, and enabling the positive displacement of fluid. Intake/suction valve assembly 2 and discharge valve assembly 3 operate between an open and closed position in response to shifting differential pressures caused by the reciprocation of plunger 4.

In one embodiment, when plunger 4 reciprocates towards the power end side B, the pressure in the internal fluid chamber 5 is such that intake/suction valve assembly 2 opens to allow fluid to enter internal fluid chamber 5, while discharge valve assembly 3 remains closed. When plunger 4 reciprocates towards the fluid end side A, the pressure differential in the internal fluid chamber 5 is such that the discharge valve assembly 3 opens to allow fluid to exit internal fluid chamber 5, while intake/suction valve assembly 2 remains closed.

Part of plunger 4 is located within fluid end housing 1, while the rest of the plunger is located outside the fluid end housing, towards power end side B. A plunger clamp 6 can be attached to power end side B of the plunger. Plunger clamp 6 is connected to a rod (not shown), through which the mechanical movement produced by the power end of the pump is transferred to the plunger. This enables plunger 4 to reciprocate axially in fluid end housing 1 between fluid end side A and power end side B. In order to provide enough space for plunger 4 to reciprocate in fluid end housing 1, a bore 7 is created within fluid end housing 1. Bore 7 has a sufficient diameter to allow plunger 4 to freely reciprocate in fluid end housing 1. Because bore 7 must have a larger diameter than plunger 4, a spatial gap is created between plunger 4 and fluid end housing 1. Packing 8 is used to seal this spatial gap, which in turn prevents the fluid from exiting the fluid end housing 1 at the power end side B.

Fluid enters the pump through intake/suction valve assembly 2, and is then held in fluid end chamber 5 before being discharged through discharge valve assembly 3. A packing 8 is placed into bore 7 to prevent this fluid from leaking out of fluid end housing 1 through the spatial gap. In one embodiment, packing 8 contains a series of seals pushed up against each other. Generally, the seals include at least a header seal and a pressure seal. These seals are generally ring shaped to match the remaining spatial gap in bore 7. The seals can be composed of any material, or any combination thereof, including but not limited to rubber, para-aramid synthetic fibers, and cotton filled rubber. The seals are placed into bore 7, and are then compressed and held in place by a self-retaining packing nut assembly 9.

As shown in the example of FIG. 1, self-retaining packing nut assembly 9 is disposed on the power end side B of fluid end housing 1. The self-retaining packing nut assembly 9 can be designed as needed to match the design of power end side B of fluid end housing 1. In one example, this section of the self-retaining packing nut assembly 9 is threaded to match the threads of the fluid end housing 1. In certain embodiments, the outer ring 11 is fully engaged with fluid end housing 1, while the inner ring 12 may be adjustable axially within the outer ring.

To prevent the seals of packing 8 from overheating during the operation of the pump, lubrication may be needed. Various lubricants can be used, including grease or oil. In certain embodiments, a lubrication port 10 is provided in the power end side B of fluid end housing 1. In the embodiment shown in FIG. 1, lubrication port 10 is placed perpendicularly to packing 8, and is used to provide access to packing 8 by a lubricant. A second lubrication port 10′ can also be provided in certain embodiments.

FIG. 2 illustrates an embodiment of the self-retaining packing nut assembly 9. Self-retaining packing nut assembly 9 is a two piece assembly having an outer ring 11 and an inner ring 12. Outer ring 11 and inner ring 12 are generally cylindrical having an axial bore therein. The generally cylindrical geometry of rings 11 and 12 allows them to fit into bore 7, and to allow plunger 4 to reciprocate within. In other embodiments, however, outer ring 11 and inner ring 12 are not cylindrical or ring shaped. In one embodiment, both outer ring 11 and inner ring 12 are metallic. Alternatively, the rings are made of any other material that can withstand the pressures associated with the application. In another embodiment, outer ring 11 and inner ring 12 can be composed of different materials. The contact between the threads of the outer ring 11 and inner ring 12 helps to decrease the possibility that inner ring 11 will back out of inner ring 12, causing the loss of compression of packing 8.

In one embodiment, inner ring 12 can be inserted into the bore of outer ring 11, as shown in FIG. 3. Then a first section 13 of outer ring 11 is threaded into fluid end housing 1. Once first section 13 is fully threaded, it can come to rest on an inner surface of fluid end housing 1. In one example, once first section 13 comes to rest a nose 27 of first section 13 axially contacts the inside of fluid end housing 1. The axial contact between nose 27 and fluid end housing 1 aids outer ring 11 lock into fluid end housing 1. In another example, once first section 13 comes to rest on an inner surface of fluid end housing 1, a second section 14 of outer ring 11, which takes the shape of a flange, can come to rest on the outside of fluid end housing 1. In some embodiments, inner ring 12 is fully inserted into outer ring 11, while in other embodiments only part of inner ring 12 is inserted into outer ring 11. Inner ring 12 can then be adjusted to sufficiently compress packing 8.

FIG. 4 illustrates an embodiment of outer ring 11 having a first section 13 and second section 14. In one example, first section 13 has a length L1 of 35 mm. First section 13 can be a cylindrical body with an axial bore therein having both an external side 15 and an internal side 16. The external side 15 of first section 13 can be threaded. In this embodiment external side 15 can be threaded to match fluid end housing 1. The threads may cover entire length L1 of first section 13, or they may only partially cover first section 13. In one example, only 25.5 mm of external side 15 is threaded, while 9.5 mm is unthreaded. When outer ring 11 is threaded into fluid end housing 1, external side 15 of outer ring 11 positively connects to fluid end housing 1. In another embodiment, external side 15 can be made to have, or carved in, any shape that will allow first section 13 to lock packing nut assembly 9 with fluid end housing 1.

In certain embodiments, internal side 16, on the other hand, does not contact the fluid end housing. Rather, the internal side 16 engages external side 24 of inner ring 12 (shown in FIGS. 6 and 8). Internal side 16 can be threaded in such a way as to resist loosening between inner ring 11 and outer ring 12. In one example, internal side 16 is threaded with M150x2 threads (not shown). This thread designation has a pitch of 2 mm, and a major diameter of 150 mm. In another embodiment, internal side 16 can be made to have any shape that will allow it to adequately engage external side 24 so as to withstand the pressures associated with the application.

Second section 14 having an external side 17 and an internal side 18, can be integrally connected to first section 13. In one embodiment, both external side 17 and internal side 18 are not threaded. Second section 14 can be a cylindrical body with an axial bore therein. In one example, second section 14 has a length L2 of 11 mm. In certain embodiments, L1 is larger than L2. As shown in FIGS. 2 and 5, second section 14 can have a mechanism used to tighten outer ring 11 into fluid end housing 1. This mechanism can utilize slots, holes, apertures, or even protrusions. In one example, second section 14 has twelve slots 19 equally spaced along external end 17. Slots 19 can take the shape of a rectangle, and having a length of 7 mm and a width of 3 mm. In other embodiments, slots 19 can have any other shape that is fit to engage a spanner or any other tool that can be used to fasten or adjust outer ring 11. In some embodiments, second section 14 may have at least one slot, while in other embodiments second section 14 can have no slots. In other embodiments, outer ring 11 can have any geometry necessary to enable a mechanism to attach to outer ring 11 in order to further engage or lock inner ring 12.

In certain embodiment, external side 17 of second section 14 has a greater diameter than the diameter of external side 15 of first section 13. This difference is created in order to help the tightening mechanisms, and causes second section 14 to take the shape of a flange. In other embodiments, external side 17 of second section 14 has mechanisms to help tighten the outer ring 11 while maintaining a diameter that is less than that of the external side 15 of first section 13. In some embodiments, when first section 13 is fully threaded, and comes to rest on an inner surface of fluid end housing 1, surface 20 of second section 14, which is the surface of second section 14 facing first section 13, makes axial contact with the outside of fluid end housing 1. In other embodiments, nose 27 of first section 13 can make axial contact with the inside of fluid end housing 1. This axial contact aids outer ring 11 to lock into fluid end housing 1, and prevents outer ring 11 from backing out. In addition, the flange shape of second section 14 allows easy access to the tightening mechanism of outer ring 11.

The diameter D2 of internal side 18 is the diameter of the axial bore of second section 14. In one embodiment, diameter D2 of internal side 18 has a smaller diameter than diameter D1 of internal side 16 of first section 13. The difference between the two diameters helps to further secure inner ring 12 into outer ring 11, and prevents inner ring 12 from backing out and colliding with plunge clamp 6. As will be discussed below, the geometry of inner ring 12 can be designed to fit into outer ring 11, so that D2 is smaller than the diameter D3 (shown in FIG. 6) of the third section 21 of inner ring 12. This difference in diameters prevents inner ring 12 from backing out of outer ring 11. In some embodiments, a round wire shape ring composed of any material that can be used to prevent inner ring 12 from backing out of outer ring 11. In other embodiments, outer ring 11 and inner ring 12 can have any geometry necessary to enable a mechanism to attach to outer ring 11 in order to further engage or lock inner ring 12.

FIG. 5 illustrates an embodiment of outer ring 11. Second section 14 takes on a flange shape in this example, and has twelve slots 19 equally spaced along external side 17. First section 13 can also be seen to have a threaded external side 15.

FIG. 6 illustrates an embodiment of inner ring 12 having a third section 21 and a fourth section 22. In one embodiment, inner ring 12 is a generally cylindrical body with an axial bore designed to be threaded into outer ring 11. Third section 21 has an inner side 23 and an outer side 24. Outer side 24 can be threaded into internal ring 11. In certain embodiments, outer side 24 can be either fully or partially threaded within outer ring 11. Outer side 24 has a diameter D3 which is larger than diameter D2 of inner side 18 of second section 14. This difference between D2 and D3 helps secure inner ring 12 into outer ring 11, thereby preventing inner ring 12 from backing out of inner ring 11 and colliding with plunger clamp 6.

In some embodiments, an adjustment tool can be used to axially adjust the inner ring 12 while installed in outer ring 11. This ensures that packing 8 remains tightly compressed within bore 7, and that fluid does not leak outside fluid end housing 1. The fourth section 22 can be designed to engage the adjustment tool. In the example shown in FIG. 6, the fourth section 22 is slotted, but can also have any other design that will allow it to engage the adjustment tool. The embodiment of FIG. 6 shows twelve slots which are equally spaced around the surface of fourth section 22. In other embodiments, fourth section 22 can have at least one slot arranged in any manner seen fit by a user. In other embodiments, fourth section 22 can have any sort of mechanism that will allow a tool to engage fourth section 22.

In the embodiment of FIG. 2, fourth section 22 is partially disposed inside outer ring 11. The surface of fourth section 22, which faces away from third section 21, can include slots 25 or any other mechanism for axially adjusting inner ring 12. Axially adjusting inner ring 12 acts to apply compression to the packing.

FIG. 7 illustrates an embodiment of one of slots 25. As seen in the embodiment, slots 25 can be generally rectangular shaped, having a length L3 and a width W1, with radiused inner corners 26, 26′. In one example, length L3 can be 14 mm and width W1 can be 13 mm. In addition, the geometry of slots 25 helps to improve the manufacturing process of inner ring 12. In other embodiments, slots 25 can be any shape, and are not limited to being rectangular. In certain embodiments, inner ring 12 can have holes, apertures, or any form of protrusion that a tool can engage to axially adjust inner ring 12.

FIG. 8 illustrates a perspective view of an embodiment of inner ring 12. Fourth section 22 can be seen as having twelve slots 25 equally spaced, having a generally rectangular shape with an open end. In this embodiment inner side 23 of third section 21 is smooth, while outer side 24 of third section 21 is threaded.

The embodiments described above help to ensure that self-retaining packing nut assembly 9 remains tightly positioned within fluid end housing 1. Doing so may ensure that packing 8 remains compressed at an adequate level. Keeping packing 8 properly compressed prevents fluid from fluid chamber 5 to leak out of the power end side B of fluid end housing 1. In addition, the embodiments described above will prevent the self-retaining packing nut assembly 9 from backing out and colliding with plunger clamp 6. This ensures the integrity of the pump, and prevents any potential damage caused by the collision of packing nut assembly 9 and plunger clamp 6.

Any surface of fluid end housing 1, outer ring 11, or inner ring 12 can be coarse threaded, fine threaded, smooth, grooved, or take any other form. The threaded and non-threaded surfaces shown the figures are only meant as illustrations of embodiments, and should in no way be taken to limit the scope of the appended claims. In addition, the figures illustrate outer ring 11 and inner ring 12 as being ring shaped. These figures, however, are only meant as illustrations of embodiments. Outer ring 11 and inner ring 12 can take on any shape that will allow them to fit into bore 7.

The features, structures, or characteristics of certain embodiments described throughout this specification may be combined in any suitable manner in one or more embodiments. For example, the usage of the phrases “certain embodiments,” “some embodiments,” or other similar language, throughout this specification refers to the fact that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present invention. Thus, appearance of the phrases “in certain embodiments,” “in some embodiments,” “in other embodiments,” or other similar language, throughout this specification does not necessarily refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

One having ordinary skill in the art will readily understand that the invention as discussed above may be practiced with hardware elements in configurations which are different than those which are disclosed. Therefore, although the invention has been described based upon these embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of the invention. 

We claim:
 1. A self-retaining packing nut assembly, comprising: a first piece having a first section and a second section, wherein the first section is configured to engage an inside of a pump housing; and a second piece having a third and fourth section, wherein the third section engages the inner surface of the first piece, wherein the second piece is configured to axially adjust inside the first piece.
 2. The self-retaining packing nut assembly of claim 1, wherein the second piece compresses a packing located inside the pump housing.
 3. The self-retaining packing nut assembly of claim 1, wherein the first section of the first piece includes a nose that engages the inside of the pump housing.
 4. The self-retaining packing nut assembly of claim 1, wherein the second section takes the shape of a flange which engages an outside of the pump housing.
 5. The self-retaining packing nut assembly of claim 1, wherein the first section has an inner side and an outer side, wherein both the inner side and outer side are threaded.
 6. The self-retaining packing nut assembly of claim 1, wherein the second section has an inner diameter that is smaller than an outer diameter of the third section of the second piece.
 7. The self-retaining packing nut assembly of claim 1, wherein the second section includes slots, holes, or apertures configured to engage a tool so as to be assembled into the pump housing.
 8. The self-retaining packing nut assembly of claim 1, wherein the fourth section includes slots, holes, or apertures configured to engage a tool so as to be axially adjusted within the first piece.
 9. An apparatus, comprising: a housing having a bore along an axis therein; a plunger configured to reciprocate within the bore along the axis; packing at least partially placed between the plunger and a side of the bore; a self-retaining packing nut assembly engaging the packing, the self-retaining packing nut assembly comprising: a first piece having a first section and a second section, wherein the first section is configured to engage an inside of a pump housing; and a second piece having a third and fourth section, wherein the third section engages on the inner surface of the first piece, wherein the second piece is configured to axially adjust inside the first piece.
 10. The apparatus of claim 9, wherein the second piece compresses the packing located inside the pump housing.
 11. The apparatus of claim 9, wherein the first section of the first piece includes a nose that engages the inside of the pump housing.
 12. The apparatus of claim 9, wherein the second section takes the shape of a flange which engages an outside of the pump housing.
 13. The apparatus of claim 9, wherein the first section has an inner side and an outer side, wherein both the inner side and outer side are threaded.
 14. The apparatus of claim 9, wherein the second section has an inner diameter that is smaller than an outer diameter of the third section of the second piece.
 15. The apparatus of claim 9, wherein the second section includes slots, holes, or apertures configured to engage a tool so as to be assembled into the pump housing.
 16. The apparatus of claim 9, wherein the fourth section includes slots, holes, or apertures configured to engage a tool so as to be axially adjusted within the first piece.
 17. A method, comprising: providing a first piece having a first section and a second section; providing a second piece having a third section and a fourth section; fastening the third section of the second piece to the first piece; inserting the first section of the first piece into a pump housing; engaging first piece with the pump housing; and axially adjusting the second piece inside the first piece to compress a packing located inside the pump housing. 